Welding in magnetic fields no longer an issue

A COMPACT welding torch enhancement and a novel power supply have made some cracks in the age-old problem of how to weld in magnetic fields.

A team of researchers from CSIRO has come up with a superior welding system that should also improve worker safety and save time, energy and money.

Previously, powerful magnetic fields - such as those found in aluminium, copper and magnesium smelters - have played havoc with any work-involving arc welding. They make welding difficult and frustrating, often causing molten metal to fly anywhere but where it should go. This makes good welds very difficult to achieve.

At the moment, welders enclose the welding area in bulky metal shields, but these give the arc only limited protection and need a two-person team - one to do the welding and one to continually shift the shield. Sometimes a welding job has to wait until the strength of the magnetic field subsides or there is downtime in the plant operation.

CSIRO's novel enhanced torch turns the job into a one-person operation and works in magnetic fields that, at more than 400 gauss, are double the strength that industry can weld in now. CSIRO has initiated patent protection.

"In combining the torch enhancements and power source we built a superior welding system, and one that is flexible, easy to use and inexpensive," says project leader, Dr Voytek Mazur.

Dr Mazur says none of the existing power sources used for arc welding had actually been designed to operate in a magnetic field. Dr Mazur's team tested different power sources in magnetic fields and found the power supply configuration that worked best.

A high-speed video recording - of up to 36,000 frames per second - was the key to finding a solution. This gave the team a unique insight into the behaviour of the arc, droplet formation and molten metal in a magnetic field.

"The video revealed a droplet's extreme behaviour in strong magnetic fields which also depends on current and voltage waveform of different power sources," says Dr Mazur. "This became crucial factors when modelling the torch enhancements."

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